Wall translation fixes and water heater EF rounding

[bpark1327]

Pull Request Description

• Remove the code that rounds up the EF and UEF of water heaters
• Relax has_rigid_ins condition
• For each side of walls, if there is only one wall, use the assembly code directly as wall assembly code

Checklist

PR Author: Check these when they're done. Not all may apply. strikethrough and check any that do not apply.

PR Reviewer: Verify each has been completed.

• Code changes (must work)
• Test exercising your feature or bug fix. Check the coverage report in the build artifacts.
• All other unit tests passing
• Update translation docs

[github-actions]

File	Coverage
All files	93%	✅
__init__.py	83%	✅
base.py	93%	✅
exceptions.py	96%	✅
hpxml2.py	98%	✅
hpxml3.py	94%	✅

Minimum allowed coverage is 83%

Generated by 🐒 cobertura-action against 5befb96

[nmerket]

Looks good.